metal:attach

(metal:attach window &key clear scale depth)

Replaces the window's content view backing with a CAMetalLayer and answers the metal:context every other function here takes. :clear is the (r g b a) a frame starts from, :scale the backing-store factor (2 for a Retina display) and :depth asks for a depth attachment -- which anything but a convex shape needs, and which every pipeline built afterwards then declares. The device comes from the layer's preferredDevice, so no C entry point is involved. Part of the metal package, a Metal drawing surface written in rontolisp over objc and loaded on first use: macOS (java -jar, the rontolisp binary, or a compiled .class / .jar; never a .wasm), with a display. See the macOS GUI guide.

CL-USER> (defvar *win* (appkit:window "metal" :width 640 :height 400 :dark t))
CL-USER> (defvar *ctx* (metal:attach *win* :clear '(0.05 0.06 0.09 1.0) :depth t))
CL-USER> (objc:send (objc:send (metal:device *ctx*) "name") "UTF8String")
"Apple M4 Max"